The present invention relates to method for the fabrication of a semiconductor device and, more particularly to a method for selective deposition of tungsten film into a contact hole by a chemical evaporating method during a process for deposition of metallic circuits on the contact hole.
It is already known that the selective deposition of tungsten film into deep contact hole by a chemical evaporating method during fabricating a metallic circuit is a very useful technique.
However, there are two critical problems in the conventional selective deposition technique of tungsten film which is to be improved.
That is,
(1) Tungsten residue 5 remains on the insulator layer 3 because of selective loss between silicon substrate 1 and the insulator layer 3, as shown in FIG. 3.
(2) Leakage current increases due to tunneling caused by enchroachment of electrodes.
In order to remove tungsten residue 5 on the insulator layer 3, it was proposed to clean the surface of the insulator before the deposition of the tungsten film after fabricating a contact hole by a plasma etching method, or to etch back the residue after deposition of the tungsten film.
However, the methods mentioned above are not desirable, because the reproducibility of the process deteriorates if there is cleaning of the surface of the insulator before the deposition of the tungsten film. Moreover, the etchback method overetched inside of the contact hole resulting in water or other chemical substances attacking during the succeeding process as shown in FIG. 4.